A control device for a vehicle hydraulic control circuit is well known that includes an automatic transmission having a shift transmission state hydraulically switched, a hydraulic control circuit that controls oil pressure supplied to the automatic transmission, and a hydraulic switch disposed on the hydraulic control circuit to detect an oil pressure supply state. One example is a power output device of Patent Document 1, for example. Patent Document 1 discloses a technique of determining a malfunction of a hydraulic control circuit based on a state of a hydraulic switch turned on/off based on a degree of oil pressure acting thereon to execute a control routine (fail-safe) at the time of malfunction if a malfunction is detected.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-16933